Coil bobbin



July 29, 1969 v A. R. HILDEBRANDT COIL BOBBIN 2 Sheets-Sheet 1 Filed May6, 1968 INVENTOR. ALBERT R. HILDEBRANDT y 1969 A. R. HlLDEBRANDT3,453,844

COIL BOBBIN Filed May 6, 1968 2 Sheets-Sheet 2 INVENTOR. ALBERT R.HiLDEBRANDT TTORNEYS United States Patent 3,458,844 COIL BOBBIN AlbertR. Hildebrandt, Reading, Ohio, assignor to Paul Smith Company, Divisionof Standard International Corporation, Cincinnati, Ohio, a corporationof Ohio Filed May 6, 1968, Ser. No. 726,809 Int. Cl. H01f 15/10, 27/30,21/06 US. Cl. 336192 5 Claims ABSTRACT OF THE DISCLOSURE Background ofthe invention My invention relates to an improved coil form, andparticularly to a new and improved coil form for electronic circuits.

Coils or inductances are used in electronic circuits to provide variousdevices such as a transformer, a tuned circuit, or some other inductivecomponent. Such coils are generally one of the more expensive items inan electronic circuit, since they must have predeterminedcharacteristics as to length, diameter, number of turns, and spacing toprovide the desired inductance. Once a coil has been designed for anelectronic circuit, the coil must then be built so that it will have thedesired predetermined characteristics. Where the coils are produced inlarge quantities, such as for home radios or television receivers, eachcoil should have the predetermined characteristics, and should be assimple and reliable as possible. Where the coil itself is small, orwhere the coil is to be used in a small or compact electronic circuit,consistently similar coils are more difficult to produce in largequantities.

Accordingly, an object of my invention is to provide a new and improvedcoil form which can be mass-produced.

Another object of my invention is to provide an improved coil form forreceiving a coil that will have predetermined characteristics, eventhough the coil form is produced in large quantities.

Another object of my invention is to provide a new and improved coilform that can be wound with a coil which will have predeterminedcharacteristics.

Another object of my invention is to provide a new and improved coilform which can be easily threaded with a tuning slug, and which canreceive other electrical components to form a compact unit that providesa desired electrical circuit.

Another object of my invention is to provide an improved coil form whichcan be wound with a coil and which can be provided with other electricalcomponents to provide a unit that is compact, that is consistent incharacteristics and properties, and that can be easily massproduced toprovide consistently similar units.

Summary of the invention Briefly, these and other objects are achievedin accordance with my invention by a coil form which takes the form ofan elongated, hollow, plastic cylinder. The

cylinder is provided with spiral grooves around its out- 3,458,844Patented July 29, 1969 ice side. Each of the grooves is separated fromthe adjacent grooves by spaced walls. The cylinder has a plurality oflongitudinal ribs extending along its inside to receive a threadedtuning slug. One or more anchor posts are provided on the outside of thecylinder. Each anchor post has a base extending from the cylinder withtwo knobs mounted on the top of the base. The knobs are spaced to form alead receiving groove between the knobs, and are shaped and dimensionedto overhang the base. The cylinder has a configuration at one end thatmates with a complementary configuration in a coil form base so that thecoil form may be mounted and firmly held.

Brief description of the drawing The subject matter which I regard as myinvention is particularly pointed out and distinctly claimed in theclaims. The structure and operation of my inventon, together withfurther objects and advantages, may be better understood from thefollowing description given in connection with the accompanying drawing,in which:

FIGURE 1 shows a perspective view of a coil form in accordance with myinvention, the coil form being mounted on a base and being provided withvarious electrical components;

FIGURE 2 shows a side elevation view of my coil form of FIGURE 1;

FIGURE 3 shows a longitudinal cross sectional view of my coil form takenalong the line 3-3 in FIGURE 2; and

FIGURE 4 shows a transverse cross sectional view of my coil form andbase taken along the line 4-4 in FIGURE 2.

Description of the preferred embodiment In FIGURE 1, I have shown oneembodiment of a coil form 10 in accordance with my invention mounted ona coil form base 11. However, it is to be understood that my coil formmay be used independently and without the base 11. For purposes ofexplaining my invention, I have assumed that the coil form 10 is to havetwo inductively coupled bifilar windings or coils, and is to beprovidedwith two diodes 14, 15 and two capacitors 16, 17 to form twotuned circuits. With reference to FIG- URES 1, 2, and 3, the coil form10 comprises an elongated, hollow cylinder 20. The coil form 10 ispreferably integral and made of a plastic which has the desiredelectrical characteristics, which can be easily molded, and which setson cooling. One such plastic may be polypropylene. The cylinder 20 hasthe desired internal and external diameters, and is provided with twosets of continuous spiral grooves 21, 22 on the outside. The grooves 21,22 have the desired length, diameter, and pitch so that wires wound inthe grooves 21, 22 will form coils having the desired inductivecharacteristics. Each of the grooves 21 is separated from the adjacentgrooves 21 by walls 23, and each of the grooves 22 is separated from theadjacent grooves 22 by. walls 24. The base of the grooves 21, 22 may befiat as shown or may be curved. I prefer that the walls 23, 24 extendradially outward beyond the base of their respective grooves 21, 22 by adistance greater than the diameter of the wire to be wound in thegrooves 21, 22 so that the wire turns are consistently separated by afixed amount of dielectric or plastic material. In addition, after wirehas been wound in the grooves 21, 22, the plastic walls 23,24 may bemelted, such as by a hot soldering iron, at precise, selected points soas to firmly fix and seal the wires in the grooves 21, 22, and thusprovide an inductance of precise size and characteristics. There may beonly one set of grooves. And, the grooves maybe arranged to providesingle windings, bifilar windings, trifilar windings or other types ofwindings.

The cylinder 20 is provided with one or more anchor posts 27. Theseanchor posts 27 preferably comprise a base 28 which extends radiallyoutward from the cylinder 20. The two projections or knobs 29 aremounted on top of the base 28. The knobs 29 are spaced to form a groove30, and the knobs 29 are dimensioned to overhang the base 28 preferablyaround all four sides. Thus, as shown in FIGURE 2, a wire or lead 31 issecurely attached to an anchor post 27 in an S-shaped configuration bypassing under one knob 29 in one direction, reversing and passing overthe top of the base 28 and in the groove 30 in the opposite direction,and reversing and passing under the other knob 29 in the one direction.

The inside of the cylinder 20 is provided with four longitudinallyextending ribs 35. The ribs 35 have a generally rectangular crosssectional configuration as shown in FIGURE 4. These ribs 35 are arrangedto receive one or more tuning slugs 36 which are made of the desiredmagnetic material, such as molded ferrite. The tuning slugs 36 haveexternal threads of a diameter slightly greater than the internaldiameter of the ribs 35. This permits the tuning slugs 36 to be threadedinto the ribs 35. The slugs 36 may be turned by a suitable tool such asan Allen head Wrench which can fit in the hexagonal opening 37 in thetuning slug 36. The plastic material forming the ribs 35 is soft enoughso that the external threads of the tuning slugs 36 cut their ownthreads into the ribs 35 as shown in FIGURE 3. Thus, the tuning slugs 36may be threaded into the cylinder 20 to the desired location to providethe desired inductive characteristics for the coils wound in the grooves21, 22. While I prefer four ribs 35 for the tuning slugs 36, more orless ribs 35 may be provided.

The coil form as described thus far is preferably made as a single,integral piece. This piece can be easily molded using various knowntechniques so that large quantities of similar coil forms can beproduced. However, if desired, parts, such as the anchor posts 27, ofthe coil form 10 may be assembled by the use of cement or otheradhesives.

The coil form 10 may be used either with or without any supporting meanssuch as the coil form base 11. However, I prefer the coil form base 11shown in the drawing since it can be provided with a socket 40 forreceiving the coil form 10. As shown in FIGURE 4, the socket 40 has aninternal configuration that is complementary to the cylinder of the coilform 10. This configuration includes a plurality of internal ribs 41which are positioned to mate with longitudinal grooves 42 positioned inthe lower end of the outer wall of the cylinder 20. When the coil form10 is to be mounted on the basell, its grooves 42 are aligned with theribs 41 and the cylinder 20 inserted into the socket 40. Thiscomplementary configuration holds the coil form 10 firmly on the base11, and prevents rotation of the coil form 10. The base 11 may be madeof plastic so that the coil form 10 can be firmly attached to the base11 by melting together portions of the plastic of the socket 40 and thecylinder 20. As shown in FIGURES l and 2, the base 11 may be providedwith various configurations in its outer wall. In particular, theseconfigurations include keying grooves 43 to hold the base 11 in a fixedrelation in an opening in a panel or printed circuit board. Theseconfigurations also include projections 44, 45 which permit the base 11to be fixed on a panel or printed circuit board. Thus, the base 11 couldbe inserted from beneath a panel until the center projections 45 passthrough the panel to hold the base 11 between the center projections 45on one side and the outer projections 44 on the other side. The base 11may also be provided with metallic terminals 46 to which wires or leadscan be soldered.

It will thus be seen that my coil form provides a new and improvedstructure for coils or inductances. My coil form permits coils to bebuilt in mass production with the assurance that each coil wound on theform will have the desired electrical characteristics. My coil form alsopermits the windings or inductances to be adjusted by removal of anypart of one or more turns, after which the remaining turns may be firmlyheld by melting the walls 23, 24. This is important in that the amountand type of dielectric material forming the coil form 10 is notdisturbed or modified, as it might be with the use of added adhesives orother materials to anchor or hold the turns or leads. The anchor postspermit various leads to be firmly and securely mounted on the coil formand insure that the mounted components and leads do not move or vibrate,with resultant changes in electrical characteristics. The internal ribspermit tuning slugs to be threaded into the cylinder and held in anydesired position of adjustment. And, the coil form permits a compact'unit of electrical components to be assembled with secure connectionsbetween the components. While I have shown only one embodiment of myinvention, persons skilled in the art will appreciate that modificationsmay be made. For example, single, bifilar, trifilar, or other types ofcoils or windings may be mounted on the coil form by providing theappropriate grooves. More or less anchor posts may be provided, and moreor less internal ribs may be provided for the tuning slugs. Differentconfigurations can be provided to hold the coil form on the base.Therefore, while my invention has been described with reference to aparticular embodiment, it is to be understood that modifications may bemade without departing from the spirit of the invention or from thescope of the claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An improved coil form for electronic apparatus and the like,comprising:

(a) an elongated, hollow, plastic cylinder;

(b) said cylinder having spiral grooves around the outside of saidcylinder along at least a portion of its length, each of said groovesbeing separated from the adjacent grooves by a wall;

(c) said cylinder having a plurality of longitudinal ribs extendingalong the inside of said cylinder, said ribs being spaced to receive athreaded tuning slug;

(d) said cylinder having at least one lead anchor post on said outsideof said cylinder, said anchor post having a base mounted on said outsideof said cylinder and extending therefrom to terminate in a base top andhaving two knobs mounted on said base top, said knobs being spaced toform a lead receiving groove therebetween and being dimensioned tooverhang said base;

(e) and said cylinder having a configuration at one end to mate with abase to hold said coil form.

2. The improved coil form of claim 1 wherein said groove walls extendoutwardly beyond the base of said grooves by a distance greater than thediameter of the wire to be wound in said grooves.

3. The improved coil form of claim 1 wherein said coil form, saidcylinder, said longitudinal ribs, said anchor posts, and saidconfiguration are molded of a single, integral piece of plastic.

4. The improved coil form of claim 3 wherein said groove walls extendoutwardly beyond the base of said grooves by a distance greater than thediameter of the wire to be wound in said grooves.

5. An improved form for an inductive Wire winding and electroniccomponents, comprising:

(a) an elongated, hollow cylinder having an inside, an

outside, and first and second ends;

(b) said cylinder having at least one continuous spiral groove formedaround said outside for at least a portion of the length of saidcylinder, each portion of said groove being formed by a pair ofcontinuous walls which are separated a predetermined distance and whichextend outwardly from said outside a distance greater than the diameterof the wire to be positioned in said groove;

(c) said cylinder having at least two longitudinal, spaced ribspositioned on said inside and extending the length of said cylinderbetween said first and second ends for receiving a cylindrical, threadedtuning element;

((1) said cylinder having at least one anchor post on said outside nearone end, said anchor post having two spaced knobs positioned on a base,said knobs being separated to form a groove therebetween and beingpositioned and dimensioned to overhang said base around all sidesthereof;

(e) and at least one longitudinal groove in said outside of saidcylinder extending from one end toward, but short of, the other end toform a configuration that (f) said cylinder, said groove and walls, saidribs, and said anchor post being an integral piece of plastic material.

References Cited UNITED STATES PATENTS 3,191,131 6/1965 Adams 336207 XFOREIGN PATENTS 866,952 5/ 1961 Great Britain.

E. A. GOLDBERG, Primary Examiner US. Cl. X.R.

mates with a complementary configuration in a 15 242-118; 336-136, 207,208

mounting base;

